A spine consists of vertebrae and intervertebral disks which are known as disks and are located between the vertebrae. Due to various causes such as diseases or accidents, spinal nerves are pressed by structures of a human body, thereby causing neurological disorders. In such a case, surgical treatment is required. In a case of vertebral fusion among the surgical treatment methods, spinal interbody fusion, in which a disk is removed and a cage, which is an artificial correction material, is inserted between the vertebrae to fuse the vertebrae, has been commonly and largely performed in recent years. In such an operation, it is important to increase a bone connection between the implanted cage and the vertebrae.
In general, the above-described spinal interbody fusion is performed by incising a back side of the human body, implanting a bone into a space between the disks, which is formed by removing the disks to the back of the vertebra, and then inserting a cage for spinal interbody fusion to cause upper and lower vertebrae to be fused with each other. A cage for anterior lumbar interbody fusion developed for this purpose causes not only the upper and lower vertebrae to be fused with each other through bone chips or bone substitutes such as an artificial bone or autogenous bone filled in an internal space thereof, but also the bones implanted in the anterior region of the disk to be fused with each other through an anterior penetration part formed therein.
As such, the cage for spinal interbody fusion serves to constantly maintain the space between the intervertebral disks until a formation of the bones is completed. Therefore, a function of quickly and stably inducing a growth of bone cells while having sufficient durability is required for the cage for spinal interbody fusion.
Korean Patent Registration No. 10-1352820 discloses an expandable cage for lumbar interbody fusion (hereinafter, referred to as ‘prior art 1’). The expandable cage for lumbar interbody fusion includes: a cage body including an upper support part for supporting a vertebra located on an upper side of the lumbar interbody, a lower support part for supporting a vertebra located at a lower side of the lumbar interbody, and a connecting part for connecting ends of the upper and lower support parts; and a sliding member slidably mounted between the upper support part and the lower support part so as to increase or decrease a gap between the upper and lower support parts.